1. Field of the Invention
This invention relates to novel single-functional and mixtures of multi-functional oligomeric performance additive compounds, their uses and polymeric compounds and compositions containing them which have enhanced oxidative stabilities, enhanced ultraviolet (UV) and light stabilities ad/or enhanced flame retardance properties.
As a result of research relating to the above-identified oligomeric performance additive compounds, the inventors have discovered that certain sulfobenzoic acids, esters and their salts have a previously undiscovered use as flame retardant additives to oligomers and polymers, and particularly as additives to aromatic polycarbonates.
2. Definitions
To aid in understanding the present invention, the following definitions of terms used in the description and/or claims are set forth:
"Single-Functional Oligomeric Performance Additive"--An oligomeric compound or composition having a single (one) type of performance additive function (e.g., UV stabilizer, light stabilizer, flame retardant or antioxidant stabilizer).
"Multi-functional Oligomeric Performance Additive"--An oligomeric compound or composition having more than one type of performance additive function.
"Non-fugitive"--An additive is non-fugitive if it does not leach out of a thermoplastic polymeric resin to which it is added, either during processing or during the end use of the thermoplastic resin to which the additive has been added.
"Oligomer"--A compound or composition having two or more repeat units in its chemical structure, but usually does not include high polymers having molecular weights above about 10,000.
3. Description of the Prior Art
Although thermoplastics (hereinafter generally referred to as "plastics") have many desirable properties and, consequently, a myriad of uses, they also suffer from deficiencies that can limit or even prevent their use in certain applications. Some of the more common deficiencies of plastics are that, 1) most can burn, 2) they are subject to oxidative degradation during processing and end use, and, 3) they are subject to degradation by light, and particularly by ultraviolet (UV) light. Therefore, in order to overcome these deficiencies, a wide variety of fire retardants, antioxidants and UV and light stabilizer additives have been developed. In order to be successful, an additive must be compatible with the plastic, i.e., it must not significantly adversely affect physical properties that are important to the end user, and it must be non-fugitive. An important consideration is that approval by the U.S. Food and Drug Administration of a plastic composition used in food and related applications is easier to obtain when it contains a non-fugitive additive.
One general approach to compatible, non-fugitive additives is to copolymerize them with the monomer(s) that constitute the plastic. This can be accomplished in several ways. For example, a vinyl group can be attached to the performance additive, which in principle, can then be copolymerized with other vinyl monomers to form a copolymer with pendant performance additives covalently attached. Alternately, performance additives possessing suitable functional groups, such as hydroxy, amino or carboxy groups, can take part in condensation polymerizations to form polymers, such as polyesters, polyamides, and polyurethanes, with attached performance additive groups.
One type of fire retardant additive for plastics is the halogenated aromatic class of fire retardants. Thus, an example of a copolymerization of a fire retardant with a vinyl group attached is the copolymerization of bromostyrene with a vinyl monomer, such as styrene. An example of condensation polymerization of a fire retardant with a suitable monomer is the copolymerization of tetrabromobisphenol A and bisphenol A with phosgene in the presence of base to form a co-polycarbonate.
One type of antioxidant additive is the hindered phenol class of antioxidants. Vinyl ester derivatives of 3-(3,5-di-t-butyl-4-hydroxypehnyl) propionic acid (HBPA) have been copolymerized to form polyolefins with antioxidant bound to the polymer. Examples of this approach are disclosed in U.S. Pat. Nos. 3,708,520 and 3,957,920. Diester derivatives of HBPA have also been used in condensation polymerizations to form polyesters with the additive attached. Examples here are in U.S. Pat. Nos. 3,943,106; 3,951,915 and 4,094,857.
There are many types of UV stabilizers for plastics, examples being o-hydroxybenzophenones, cyanocinnamates, hindered amine light stabilizers (HALS), 2-hydroxyphenylbenzotriazoles, dialkyl benzylidenemalonates, and oxanilides. Vinyl ester derivatives of 2,4-dihydroxybenzophenones (DHBP) have been both homopolymerized and copolymerized. This work is described in U.S. Pat. Nos. 3,313,866; 3,365,421; 3,391,110; and 4,304,895. In addition, suitably substituted DHBP derivatives such as 2-hydroxy-4-(2-hydroxyethoxy) benzophenone, have been used in condensation polymerizations as described in U.S. Pat. Nos. 4,418,000 and 4,264,680.
In the case of the cyanocinnamate class of stabilizers, various vinyl ester derivatives of 2-cyano-3,3-diphenyl-2-propenoic acid have been copolymerized with different vinyl monomers as described in U.S. Pat. Nos. 4,276,136; 4,207,253 and 4,202,834. vinyl monomers of HALS are also known and have been copolymerized with a variety of monomers. Examples can be found in U.S. Pat. Nos. 4,175,970; 4,210,612 and 4,294,949. there are also examples of HALS compounds used in condensation polymerizations as disclosed in Canadian Patent 1,016,295. In these examples, a HALS is attached to an ethylene oxide oligomer, which in turn is copolymerized with diethylene glycol terephthalate to form a polyethylene terephthalate polyester with a HALS group incorporated into it.
Although the above approaches do incorporate a non-fugitive additive into a plastic, there are still some drawbacks. For instance, additives with a vinyl or other suitable functional group may not be readily available, the reactive additive may not copolymerize easily with the desired monomers, or the resultant copolymer may be deficient in other physical properties (such as impact strength) that are important to the end user.
Instead of the foregoing approaches for incorporating non-fugitive additives in plastics, in accordance with the inventive concept of the present invention, a performance additive is attached onto an oligomer having a molecular weight of less than about 10,000, typically, less than about 5,000, and then the oligomer-additive adduct is blended with the desired polymer. By judicious choice of oligomers, the compatibility of the oligomer-additive adduct with a polymer can be assured, and with relatively high molecular weight of the adduct, its non-fugitive nature in a polymer blend is also assured.
In order to use this approach, suitable reactive functional groups at one end, at both ends and/or on branch points along the oligomer are required. Thus, mono-, di- or polyadducts can be prepared and blended with the chosen polymer. Examples of suitable functional groups on an oligomer are groups such as acid halide, amino, anhydride, carboxy, chloroformate, epoxy, hydroxy, and isocyanate.
These same types of functional groups may also be present on the additive. Thus, chemical attachment of the additive onto the oligomer is assured by incorporating functional groups onto the additive that are known in the art to react with those on the oligomer. One example is an additive with acid halide (chloride for instance) groups being reacted with an oligomer possessing hydroxy groups to form an oligomer-additive adduct held together by the resultant ester linkages.
Polymers including fire retardant functional groups are known in the prior art. One particular type has aromatic sulfonic acid salts as the retardant functional group. These are effective fire retardants for aromatic polycarbonates (PC's). Examples of polymeric salts are polysulfonated salts of polysulfone and polysulfone copolymers which are described in U.S. Pat. Nos. 4,033,930; 4,092,294 and 3,948,851. In U.S. Pat. No. 3,978,024, sulfonated salts or aromatic polycarbonates are disclosed, while in U.S. Pat. No. 4,032,506 polysodium poly(2,6-di-methyl-phenylene oxide) polysulfonate is mentioned. Sulfonated salts of polymers with aralkenylidene moieties are disclosed in U.S. Pat. Nos. 3,940,366 and 3,933,734. In U.S. Pat. No. 3,951,910, sulfonic acid salts of a variety of polymers are described. The above examples all share the common thread of a polymer being sulfonated with a suitable sulfonating agent such as sulfur trioxide or fuming sulfuric acid. However, there are only a few examples of a sulfonic acid salt being incorporated into a polymer using other types of reagents.
The prior art does not disclose the use of 2-sulfobenzoic acid compounds, such as 2-sulfobenzoic acid cyclic anhydride and related compounds of the present invention as reagents for polymers or oligomers containing mono-, di-, and polyhydroxy functional groups. When this additive and a hydroxy or amino oligomer are allowed to react in the presence of base, the resulting compounds are polymers or oligomers which have one or more arylsulfonic acid salt groups attached to them. Such compounds are fire retardant additives according to the present invention useful for aromatic polycarbonates (PC's).
Thus, in the case of sulfonic acid salt fire retardants, it is believed that the closest prior art to the present invention is disclosed in U.S. Pat. Nos. 3,933,734 and 4,285,855 where propane sulfone is used as an endcapping agent for polymers. The products are polymers endcapped with alkylsulfonic acid groups. These are fire retardant additives for aromatic (PC's).
In the case of UV stabilizers, the closest prior art to the present invention is believed to be disclosed is U.S. Pat. Nos. 4,260,719 and 4,247,474 where cyanocinnamate types of UV stabilizer, 1-cyano-3,3-diphenyl-2-propenoyl chloride and 2-(chlorocarbonyloxy)ethyl-2-cyano-3,3-diphenylacrylate are used to endcap polycarbonate.
In the case of antioxidants, the closest prior art to the present invention is believed to be disclosed in U.S. Pat. Nos. 3,944,594 and 4,032,562, and Canadian Patent 995686 where polyethylene oxide esters of HBPA are disclosed as antioxidants for plastics. In U.S. Pat. No. 3,819,573 HBPA was attached to aliphatic polyesters or polyamides by heating either it or its methyl or ethyl ester derivatives in the presence of suitable monomers or oligomers, such as caprolactone and caprolactam and oligomers therefrom.
The prior art does not disclose the endcapping of aliphatic polyester, polycarbonate, polyamide, polyurethane and polyurea oligomers. In addition, polyether-polythioether co-oligomers, amino terminated plyethers and hydroxy- or amino-terminated silicones or silicone copolymers have not been disclosed, nor have been disclosed hydroxy terminated polyethylene oligomers, amino- or hydroxy-terminated polybutadiene oligomers, amino- or hydroxy-terminated polybutadiene-acrylonitrile oligomers, or styrene-allyl alcohol co-oligomers. In this invention, the above oligomers can be endcapped with suitable fire retardants, antioxidants, light and/or UV stabilizers, and the resultant oligomer-additive adduct can be blended into a compatible polymer so as to improve the fire retardance and/or oxidative stability and/or light and/or UV stability of the polymer.